Recently development and use in practice of magnetic recording devices using rotary heads, such as 8 mm video tape recorders, digital tape recorders, etc. have been advanced.
In such devices the construction is apt to be complicated and large with respect to that of the conventional fixed head type devices, because, in addition to the requirement of the space for locating the rotary head and thesspace for the driving system necessary for utilizing the rotary head, a tape loading mechanism drawing-out a tape loading block, a subblock, guide posts, a pinch roller, etc. necessary for winding a tape around the rotary head are inevitable.
For this reason it is tried to reduce the size while simplifying the construction in each part and in particular, as one of these trials to reduce the number of driving motors by driving 2 driving systems having different timings by means of a single driving motor.
Heretofore, as such a mechanism for branching the driving force, are used a gear mechanism, by which a cam is disposed on a driving gear, which drives a driving system by engagement of gears, and the second driving system is driven by this cam, a gear mechanism, by which two intermittent gears are disposed on both the sides of the driving gear so as to be driven alternately, and so forth.
However, in the former gear mechanism using a cam gear, since the first driving system is driven by a certain rotation angle of the cam gear and the second driving system is driven by the cam for the remaining driving rotation angle, in the case where the remaining driving rotation angle is small, the cam driving is not possible and thus its field of utilization is extremely restricted. On the other hand, in the latter gear mechanism using intermittent gears, since it is so constructed that, after the drive of the first driving system by means of the first intermittent gear, it is held at its intermittent position, while the second intermittent gear is driven, means for holding the intermittent gear at its intermittent position, means for calling-in it from its intermittent position, etc. are necessary. Therefore the construction is apt to be complicated and large and in addition, it is necessary for the driving motor to be switched on and off during the interval between the operations of the two driving systems, depending on the operation timing of the two driving systems. Thus it has problems that the electrical connection is complicated because of this fact, etc., which finally restricts its field of utilization.
Such problems as described above existed not only in the magnetic recording devices using the rotary head but also in electric apparatuses in general, which are provided with a plurality of driving systems using a single driving motor, and for which it is required to reduce the size and to simplify the construction.